This invention relates to an abrasive bond having improved physical properties.
1. Field of Art
The abrading material of the invention comprises a binder and abrasive grain as known in the art, improved by the addition of compressible plant-fiber particulate. This particulate is useful as a grain-spacer in both resin-bonded and cement-bonded abrasives, provides resilience and strength to normally very brittle cement bonds such as magnesium oxychloride bonds, is relatively inexpensive, and is environmentally sound.
2. Discussion of Related Art
Grain-spacers are commonly used in abrasive bonds to improve physical properties of the bond, depending upon the spacer employed. Cement bonds, especially, tend to suffer from expansion and contraction in the course of use, and various materials, notably cork, have been used to improve bond resiliency.
U.S. Pat. No. 426,994 discloses such an abrasive tool composition comprising a rubber binder, abrasive grit, and cork granules which provide a grinding and polishing wheel "having sufficient softness to hold the abrading particles and sufficient elasticity to yield and act kindly . . . , on the surfaces to be treated combined with the required firmness and strength". U.S. Pat. No. 898,381 to Matrison describes a "cork concrete" flooring material comprising cork particles lightly bound with a magnesium oxychloride cement which is "very elastic and springy". U.S. Pat. No. 2,231,123 refers to magnesium oxychloride flooring compositions containing cork which "are highly resilient but their strength has been reduced to the point where they cannot give satisfactory performance".
U.S. Pat. Nos. 1,668,475 to Wescott and 608,877 to Lattimore describe abrasive bonds reinforced with plant-derived fibers. U.S. Pat. No. 2,231,123, however, describes at length the difficulties of forming a strong, resilient cementitious bond with such fibers. As stated by the patentee, plant fibers previously proposed for imparting resiliency to magnesium oxychloride cement bonds have, for example, been found to be unstable in the cementitious composition, or difficult to incorporate. Other fibers either imparted little resiliency, or seriously detracted from the soundness and strength of the bond. Wood fibers in particular are stated to "very appreciably [reduce] the water-resistance and strength and soundness of the cementitious compositions . . . ". The patentee speculates that the tensile strength of cementitious bonds containing plant fibers depends to an appreciable extent upon the ability of the individual fibers to move on each other and distribute strain, and addresses these problems by using reclaimed cotton tire cords in a magnesium oxychloride cement composition preferably containing copper powder and silica. The tensile strength of comparison compositions containing cork granules instead of tire cord fibers were substantially weaker.